The present invention relates to an infrared reflecting black pigment, a paint and a resin composition, and more particularly, to an infrared reflecting black pigment which is capable of providing a heat-shielding paint containing no harmful elements and exhibiting an excellent infrared reflecting property, and a paint and a resin composition containing the pigment.
In roads, buildings, storage tanks, automobiles, ships, etc., which are used or located out of doors, an inside temperature thereof is increased when exposed to solar radiation. For this reason, an outside surface of buildings, automobiles, etc., has been painted with a white to light color to reflect sunlight thereon, thereby enhancing a heat-shielding effect thereof to some extent.
However, in particular, roofs of buildings exposed outside are frequently painted with a deep to black color to make stains or contamination thereon unremarkable. Buildings, automobiles, etc., whose outside surface is painted with a deep color to black color, tend to absorb sunlight as compared to those having an outside surface painted with a light to white color, and tend to suffer from considerable increase in inside temperature when exposed to solar radiation. Such a high inside temperature of buildings, automobiles, etc., is undesirable for transportation or storage of products.
From the standpoint of saving energies required for preventing global warming-up problems, it has been strongly demanded to suppress the increase in inside temperature of buildings, automobiles, etc., whose outside surface exhibits deep color to black color.
In order to prevent the increase in inside temperature of buildings, automobiles, etc., whose outside surface is painted with a deep color to black color, there have been conventionally used heat-shielding black paints. For example, there has been proposed a black calcined pigment having a spinel structure composed of CoO, Cr2O3 and Fe2O3 (refer to Japanese Patent Application Laid-Open (KOKAI) No. 2000-72990). However, the black calcined pigment contains Cr as a harmful substance and has an average reflectance of less than 35% in an infrared wavelength range of 780 to 2500 nm, and, as a result, may fail to exhibit a sufficient heat-shielding effect.
There has been proposed a black pigment in the form of a calcined pigment containing Fe2O3 as an essential component together with Cr2O3, Mn2O3 or NiO (refer to Japanese Patent Application Laid-Open (KOKAI) No. 2001-311049). However, the black calcined pigment contains Cr as a harmful substance.
There has also been proposed a black composite oxide made of a rare earth element, an alkali earth metal and iron (refer to Japanese Patent Application Laid-Open (KOKAI) No. 2004-83616). However, the black calcined pigment may fail to exhibit a sufficient heat-shielding effect.
In addition, there has been proposed a strontium iron oxide perovskite having an excellent blackness (refer to Japanese Patent Application Laid-Open (KOKAI) No. 2000-264639). However, the strontium iron oxide perovskite has an average reflectance of not more than 10% in a visible light wavelength range of 250 to 780 nm and an average reflectance of less than 35% in an infrared wavelength range of 780 to 2500 nm and, therefore, may fail to exhibit a sufficient heat-shielding effect.
Further, there has been proposed a magnesium/aluminum-containing iron oxide having an excellent blackness (refer to Japanese Patent Application Laid-Open (KOKAI) No. 2003-238164). However, the iron oxide has an average reflectance of not more than 10% in a visible light wavelength range of 250 to 780 nm and an average reflectance of less than 30% in an infrared wavelength range of 780 to 2500 nm and, therefore, may fail to exhibit a sufficient heat-shielding effect.